A contact type sensor is known using a sliding resistor and a sliding contact. With this conventional rotational angle sensor alone, a procedure is performed of regulating and confirming an output corresponding to a rotational angle during the mounting of the sensor to a throttle valve. In this final step, the sensor side is rotated relative to the throttle valve side by utilizing a long hole formed in the rotating direction. Thereafter both are fixed to each other.
In the above conventional sensor, however, it is necessary that mounting adjustment be done at least twice between the throttle valve side and the sensor side, thus giving rise to the problem of too many adjusting steps. Besides, the regulation of an output gradient gain is performed only in a discrete state of the sensor and the final mounting of the sensor to the throttle valve side is performed by a one-point adjustment, with the result that the rotational angle detecting accuracy is low. Further, in the case of a contact type sensor using a sliding resistor and a sliding contact, it is difficult to diminish variations in the printing accuracy (e.g., film thickness and width) during the fabrication of the resistor.